The present invention relates generally to a liquid tank filler cap and valve assembly, and in particular to a vented fuel tank cap having plurality of vent passages which discharge through common outlet openings and which is attached to the filler tube of the fuel tank by a cam actuated connector. The cam actuated connector includes a ramp-shaped cam surface with a locking notch that is engaged by a cam follower pin in the closed position of the cap to provide a positive indicator that the cap is completely closed to prevent fuel leakage. The fuel tank cap is especially useful for vehicles such as diesel engine trucks and the like. Such cap vents fumes from the tank through a first passage which is normally open but contains a float valve which closes for preventing liquid fuel from spilling in the tank when it tips beyond a predetermined angle of inclination, through a second passage including a pressure relief valve which opens when the pressure within the tank exceeds a predetermined pressure, and through a third passage including fusible metal plugs, which melt to vent the tank above a predetermined temperature such as might be encountered in a fire.
It has been previously proposed in U.S. Pat. No. 4,796,777 of Russell D. Keller, the present inventor, issued Jan. 10, 1989, to provide a vented fuel tank cap with a pressure relief valve and a float valve, as well as with a fusible element for venting the tank above a predetermined temperature through a hole in the top of the cap. However the apparatus shown in such patent is more complicated and expensive than the present invention. In addition it has the disadvantage of connecting the fuel tank cap to the top of the filler tube by means of threads which can cause difficulty in releasing the cap. Thus, when the threads get dirty due to dust, mud and other foreign materials, the cap sometimes sticks and is very hard to remove. Similarly, when the threads have moisture contained therein the cap may freeze closed. These problems are overcome with the vented fuel tank cap of the present invention by employing a cam actuated connector to attach the cap to the top of the tank filler tube for quick and easy removal. Also with the present cap three vent passages are provided including a first passage which is normally open for venting the tank at normal pressure and temperature, a second passage containing a pressure relief valve for venting the tank above a predetermined higher pressure, and a third passage normally closed by fusible metal plugs, which melt above a predetermined temperature. These three passages have common outlet openings for venting all passages through the cam actuated connection between four cam actuators spaced around the periphery of the filler tube. In addition the pressure relief valve is more efficient because it employs a larger vent opening around the entire periphery of the tank fill tube, while the above described prior pressure relief valve vents through a smaller opening in the top of the cap.
It is also previously been proposed in U.S. Pat. No. 4,162,021 of Crute issued July 24, 1979, to provide a pressure vacuum release fuel tank cap with a roll over gravity operated safety valve including a metal ball which closes a vent valve to prevent spillage when the truck rolls over. In addition, this vented fuel tank cap is provided with a cam lock connector for fastening the cap to the inside of the filler neck tube to resist high pressure like a radiator cap. However this has the disadvantage that the cam surface extends into the filler neck and is exposed to the corrosive effects of the fuel contained in such filler neck. The pressure relief valve employed in such cap is much more complicated construction and employs two additional operating springs which are separate from the spring used for closing the cap. In addition there is no disclosure of the use of three vent passages having a common outlet which contain three different valves such as a pressure relief valve, a float valve, and a fusible plug valve to provide safety venting under several different conditions in the manner of the present invention. Also the vent opening for the pressure relief valve is of much smaller area than that of the present invention.